The father of the deceased, Yusuf, 50, who was working with them, and a fireman who went to rescue them, have been admitted to a city hospital after they too experienced suffocation.
While a city police statement said it was a sewage plant, a police officer who visited the tank, a Delhi civil defence volunteer and Yusuf, who was recuperating in a city hospital, told IANS that it was a septic tank and not sewage tank.
Delhi Water Minister Rajendra Pal Gautam in a tweet on Saturday evening also termed it a septic tank.
According to the city police, Yusuf and his sons Jahangir, 24, and Ijaz, 22, went to clean a sewage plant at Aggarwal Fun City Mall in Anand Vihar in east Delhi on Saturday. The incident happened around 1 p.m.
When asked about the deaths, Deputy Commissioner of Police Nupur Prasad told IANS that the two did not have any safety equipment on them and that no one had been arrested so far.
A senior police officer privy to the case told IANS that the "mall authorities" had said that maintenance work was outsourced and they were not responsible for it.
"We'll have to look into the terms and conditions and documentation to see who is responsible for the deaths," the officer said.
The deceased brothers were residents of Sahibabad in Uttar Pradesh, which borders Delhi, according to police.
"They collapsed after being suffocated due to the gas and a fireman Mahipal who went to rescue them also inhaled the gas," Prasad said.
Police said though they were rushed to a hospital, Jahangir was declared brought dead and Ijaz also died later.
The DCP said Yusuf and Mahipal were undergoing treatment and added that a case had been registered.
Jahangir was the father of two children, while Ijaz had three children, with the youngest one being a seven-month-old boy.
Last Sunday, three persons had died after inhaling toxic gases while cleaning a sewer in Lajpat Nagar area of south Delhi.
Similarly, last month four persons had died in the national capital after inhaling poisonous gases as they entered to clean a water harvesting tank in Ghitorni area of south Delhi.
In both cases, lack of safety equipment for the workers was said to have led to the tragedy.
On Saturday evening, Delhi Water Minister Rajendra Pal Gautam said in a tweet: "Though we have no control on private buildings, we Will take stern action against the violators."
The minister also said that he was constituting a "vigilance committee to monitor such illegal activities and stop such acts".
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
About VDC
Doraiah Chowdary Vundavally is a Software engineer at VTech . He is the news editor of SocialNews.XYZ and Freelance writer-contributes Telugu and English Columns on Films, Politics, and Gossips. He is the primary contributor for South Cinema Section of SocialNews.XYZ. His mission is to help to develop SocialNews.XYZ into a News website that has no bias or judgement towards any.